In engine technology injection valves are used for the precisely dosed supply of fuel. Particularly in the case of motor vehicles particularly high demands are made on injection valves with respect to a quantitatively very precise supply of the fuel, so as to obtain a very good and complete combustion of the fuel in the engine. This is more especially necessary in order to attain and maintain the strict requirements with respect to the exhaust values and engine efficiency.
In connection with the manufacture of injection valves it is known that at the end of the manufacturing process they are tested and precisely set with respect to the flow through them. For this purpose use is made of a measuring device, where the injection valve located therein is subject to the action of a test fluid under a specific pressure. In the measuring device the volume flow, also known as the through-flow or flow, is passed through the injection valve. The determined flow value is subsequently compared with the desired flow of the injection valve.
If a difference is detected between the actual and the desired value, the opening mechanism of the injection valve is adjusted in such a way that the opening time of the valve and consequently its flow is changed. The measuring cycle is then repeated and again a fluid under a constant pressure is passed through the valve and the flow which occurs is measured by a flow sensor. If a difference is still found between the actual and the desired value, the previously described setting and subsequent measuring process is repeated until the actual value reaches the desired value or at least a desired value range.
Generally between 60 and 80 seconds are required for setting an injection valve. Approximately 60 to 75% of the total testing, checking and setting process is taken up by the measurement and stabilization times.
An important reason for the/long measuring times is due to the flowmeters. Use is generally made of continuously measuring flowmeters on a volumetric meter basis, e.g. flow measuring turbines or geared pumps. With these measuring means the number of pulses corresponding to the flow quantity are summated by a suitable counter within a fixed time interval or gate time. Thus, a measured volume flow value is obtained, which can be defined as pulses per time unit. In order to obtain with such volumetric meters sufficiently accurate results, generally measuring times between 3 and 10 seconds per measuring process are required. The measuring times are a function of the flow quantity and the structure of the fluid circuit.
Such flowmeters have a relatively complicated construction and are expensive to buy. In addition, due to the integrated measuring process, it is not possible to detect unstable injection valves. Overall the conventional testing and setting procedure for injection valves is relatively time-consuming, the capacity of a measuring and setting device being limited to 40 to 60 injection valves per hour. This leads to correspondingly high plant costs for each injection valve. For the manufacture of large numbers a relatively large number of measuring devices is needed, which requires correspondingly high surface and investment costs.
DE 41 23 787 A1 discloses a fuel injection valve and a method for setting a fuel injection valve, the statically delivered fuel quantity supplied during the stationary open state of the fuel valve being set in that in a first method step on an already fitted fuel valve the actual quantity of the delivered fuel is measured with the fuel injection valve completely open and is compared with a predetermined desired quantity, whilst in a second method step the free flow cross-section of a restrictor is modified until the delivered actual quantity corresponds to the predetermined desired fuel value. This requires two time-succeeding working steps, in which in each case a volume is measured and in which the instantaneous volume flow and instantaneous pressure remain unknown.
DE 37 23 698 A1 discloses a method for the manufacture of a fuel injection valve, a component provided with several spraying openings in the form of a small plate being provided, in which the spraying openings are formed by erosion and the setting of the static flow quantity is carried out through the spraying openings by hydroabrading thereof, i.e. by scavenging said openings with a fluid abrasive medium. This method is performed once prior to the fitting of the valve and is unusable for valve setting purposes when the valve is being used in the engine.
De 33 28 044 A1 discloses a device for setting a plurality of injection units, particularly injection valves for multicylinder diesel engines. This known device is fitted at a corresponding point on the engine for the purpose of setting the injection valves and is removed again after setting an optimum basic setting. The quality of this basic setting is determined by establishing a smooth idling of the engine.
EP 5 09 455 A1 discloses a device for producing a precision fluid flow, particularly for testing injection valves. In this known device, which serves for the time-average quality control of injection valves, the liquid pressure is set in accurate and time-constant manner as a measured variable over the liquid flow. The setting of the valve or the corresponding quality control of the valve does not take place when the valve is fitted.